Periodontal disease has assumed primary importance as the cause of loss of supporting alveolar bone and teeth. However, it has been shown that tetracycline, when placed within a diseased periodontal pocket, can reduce populations of the disease-causing pathogens. Our purpose is to develop and test a tetracycline reservoir which will fill the pocket, conform to its contours, and retain its physical integrity for 7-10 days, during which time the active agent is continuously available to the diseased tissue. The device will consist of a thixotropy will permit the matrix material to be injected into he pocket as a fluid which will then gel when left undisturbed; and H+ - bonding will harden the gel. The selected formulation will be tested in four beagles with existing periodontitis. Assuming each dog has 5 pockets, 12 pockets will be filled with the drug formulation, 4 with a placebo gel and 4 pockets will remain empty. The extent of active disease will be estimated on days 0 & 7 using standard clinical criteria and a bacterial analysis (DMDx). Crevicular fluid flow and fluid drug concentration will be measured as a function of time. Residual gel will be removed on Day 7 and tested for residual drug and residual gel material. Biopsies will be taken from selected sites and examined for epithelial ulceration, inflammatory infiltration into underlying connective tissue, and presence or absence of giant cell responses.